1. Field of the Invention
This invention relates to carrier apparatus for retaining and positioning sheet-like microfilm in viewcopier apparatus.
2. Description of the Prior Art
In general, in microfilm viewer or viewer-copier and the like apparatus, the microfilm is customarily illuminated by a light source, so that images recorded on the film are enlarged and projected onto a screen or a photosensitive member through a projecting lens.
Further, microfilm may be classified as either rolled film type, in which the frames carrying images thereon are arranged linearly, or sheet film type, in which the frames carrying images thereon are arranged two-dimensionally. Sheet type microfilm dictates the use of a carrier apparatus which moves two-dimensionally, with the microfilm sheets held flatwise, to bring a specific frame carrying a desired image thereon into a projecting position.
Such carrier apparatus consists of a moving body which moves the film and guide members which guide the aforesaid moving body. In the case of document-support moving type electrophotographic reproducing apparatus, there are interposed ball bearings or bearings between the moving body and the guide members to provide smooth movement for the moving body. However, with ball bearings inserted between the moving body and the guide members, the ball bearings also move due to the movement of the moving body, and irregular movement of the ball bearings results. The irregular movement of the ball bearings causes looseness between the moving body and the guide members, or hinders the smooth movement of the moving body. But with bearings interposed between the moving body and the guide members, the sizes of the moving body and guide members having shapes suited for holding the bearings have to be increased, and also there are required a plurality of bearings in an attempt to minimize the looseness of the moving body during its movement.
To prevent looseness between the moving body and guide members during the movement of the moving body to thereby provide a smooth movement therefor, the respective bearings should be adjusted. However, considerable difficulty is incurred, because of the complicated shape of the moving body or the guide members. This is particularly true with the case of viewer-copier and the like apparatus for use in microphotography. In other words, upon rapid but accurate movement of a specific frame carrying a desired image thereon to a projection position, the looseness between the moving body and the guide members, or the effect of the failure to provide a smooth movement for the moving body, causes a blur or positional misalignment of a projected image. This necessitates repetitive position-compensating operations to eliminate such defects in the moving body.
Moreover, since there has arisen a tendency to incorporate several hundreds of frames, which carry a great amount of data, in a single sheet of film, there has to be used a projecting lens having a high magnification. Projecting lenses providing such a high magnification enlarge an image with the concomitant effects of the looseness between the moving body and the guide member or with the effect of non-smooth movement of the moving body. Thus, there is an improper projection of an image onto a screen due to the positional misalignment of a desired image, or there is an out-of-focus condition of part or the whole of the projected image every time the moving body is moved. For this reason, a plurality of operations and many man-hours are required for the projection and reproduction of an image, with an accompanying increase in the mental fatigue of the operator.